I was going to give a big rant about this topic, but I'm not going to spill my personal business right now.  

Please don't answer this question if you've never lived with anyone for a decent amount of time (a year or more).  This is a genuine question and I'm not interested in TdV fodder.  Also, if you've never lived with someone, you might have ideas.... but it all changes when you're face with reality, trust me.

If you've lived with someone for more than a year (other than immediate family), how do you define your space?
Who is in charge of what areas?  Do you have a 'mine only/ don't touch' policy/ understanding?  What happens if you straighten your partner's area(s)?  Or does it matter to you at all?  Any complains from you or your partner about one of you invading the other's "space"?  Did you talk about it and figure it all out, or did it just come naturally and with time?

I would probably have had a lot healthier relationship in the past if there would have been more of this "mine only" stuff and areas. Maybe not though?

I was in charge of all areas and I cannot recall that there were ever mine only/don't touch items and rooms. If there had been and my partner would've straightened those areas I think I would view it as my partner taking care of me. (Unless the straightening was accompanied with some sort of argument)

What a broken mess...

I'm kind of surprised I only got one response for this.  I'd really like some more input, as it's an issue that crops up in my own family quite often. 

I guess I can briefly give an example to hopefully spur more conversation.

I have been asking my husband since January to file our taxes.   However, as usual.. he decided to wait until the last day.  I had decided to do a 'spring cleaning' the week before, and in the middle of it my husband freaked out over his paperwork, asking me not to touch it.  Since I know that he's.... well... quite paranoid over things like that (He won't even tell me passwords in our own home in case -someone- is somehow listening in...), I did NOT touch his paperwork. I know for a fact I didn't... I cleaned every inch of the house but refused to touch that bundle of papers.

However, when it came time to file the taxes in April... the DAY taxes were due... guess what?  His papers were no longer there.  And guess who got the blame?  My husband started getting very upset, claiming that I must have moved those papers.  He proceeded to complain, insisting that I never give him a single square inch of our household, and that I try to control every last nook and cranny of our residence.  For those of you that don't know me well... this couldn't be further from the truth. However, I feel as though he developed these feelings due to me cleaning the house and organizing it.

I know I could just clean -part- of the house, but then the other parts would never get cleaned... (Trust me... I did a little experiment which proved it, running from April 16th to about a week ago.)  But why should I have to define what -parts- of the house I get to clean anyways?

Do any other couples have problems like this and how were they resolved?

My wife and I live in a 1200 sq ft house with a baby and a dog.  We don't have defined areas that belong to only one or the other of us.  I have a spot in the basement where I may play video games but my wife doesn't go there because it is not pleasant and she doesn't care for being in basements, even finished ones.

We cohabitate very well with each other.  We have couch space and we usually pile up on each other.  The only serious off-limits is when a bathroom door is closed.  My wife doesn't bother me when I have the door shut and I don't bother her either.  Other than that, we're fine to share all sorts of space with each other.  We both clean (I vacuumed and dusted today) and we take care of each other's stuff.  We also always keep our own stuff neat and clean.  We don't have a spotless house but we certainly don't have things lying around very much.

What you're talking about sounds like something much deeper than responsibility over who has to achieve what from a room standpoint.

I don't know your relationship with each other but something like this doesn't just spring out of nowhere and it's generally not a result of who's space is where.  My relationship allows everyone to use all space with respect to everyone else.  

There's more going on.  What's up?

For the most part we don't really have defined areas, unless there is a mess... then it is declared mine even when half of it is his. We each have our own area where our laptops are that are sorta "our spots" but neither of us care if the other uses it when we are not.

His mother lives with us, and she does the majority of the cleaning since we pay bills, the only areas she leaves alone are the kitchen table (where the messes of old mail happen), the litterbox (our cats, our mess), our bathroom and bedroom (beyond vacuuming).

Luckily we have a pretty defined system of where important papers go that is communal, and that makes it easy to avoid fights over such things. I do think that you should really get on him to file earlier next year because waiting until Tax Day to file is just asking for trouble.